Not at home in a youth centre (3)
I believe the answer is:
out
'not at home' is the definition.
(I've seen this before)
'in a youth centre' is the wordplay.
'in' indicates a hidden word.
'OUT' is hidden in the letters of 'youth centre'.
(Other definitions for out that I've seen before include "SECOND PART OF 11" , "On strike - dismissed - unconsciousout" , "Away; into public domain" , "impossible" , "Known" .)